Method for manufacturing gallium and nitrogen bearing laser devices with improved usage of substrate material

ABSTRACT

A plurality of dies includes a gallium and nitrogen containing substrate having a surface region and an epitaxial material formed overlying the surface region. The epitaxial material includes an n-type cladding region, an active region having at least one active layer overlying the n-type cladding region, and a p-type cladding region overlying the active region. The epitaxial material is patterned to form the plurality of dies on the surface region, the dies corresponding to a laser device. Each of the plurality of dies includes a release region composed of a material with a smaller bandgap than an adjacent epitaxial material. A lateral width of the release region is narrower than a lateral width of immediately adjacent layers above and below the release region to form undercut regions bounding each side of the release region. Each die also includes a passivation region extending along sidewalls of the active region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/675,532, filed Aug. 11, 2017, which is a continuation of U.S.application Ser. No. 15/173,441, filed Jun. 3, 2016, which is acontinuation of U.S. application Ser. No. 14/176,403, filed Feb. 10,2014, now U.S. Pat. No. 9,362,715, the entire contents of both of whichare incorporated herein by reference in their entirety for all purposes.

BACKGROUND

In 1960, the laser was first demonstrated by Theodore H. Maiman atHughes Research Laboratories in Malibu. This laser utilized asolid-state flash lamp-pumped synthetic ruby crystal to produce redlaser light at 694 nm. By 1964, blue and green laser output wasdemonstrated by William Bridges at Hughes Aircraft utilizing a gas laserdesign called an Argon ion laser. The Ar-ion laser utilized a noble gasas the active medium and produced laser light output in the UV, blue,and green wavelengths including 351 nm, 454.6 nm, 457.9 nm, 465.8 nm,476.5 nm, 488.0 nm, 496.5 nm, 501.7 nm, 514.5 nm, and 528.7 nm. TheAr-ion laser had the benefit of producing highly directional andfocusable light with a narrow spectral output, but the wall plugefficiency was <0.1%, and the size, weight, and cost of the lasers wereundesirable as well.

As laser technology evolved, more efficient lamp pumped solid statelaser designs were developed for the red and infrared wavelengths, butthese technologies remained a challenge for blue and green and bluelasers. As a result, lamp pumped solid state lasers were developed inthe infrared, and the output wavelength was converted to the visibleusing specialty crystals with nonlinear optical properties. A green lamppumped solid state laser had 3 stages: electricity powers lamp, lampexcites gain crystal which lases at 1064 nm, 1064 nm goes into frequencyconversion crystal which converts to visible 532 nm. The resulting greenand blue lasers were called “lamped pumped solid state lasers withsecond harmonic generation” (LPSS with SHG) had wall plug efficiency of˜1%, and were more efficient than Ar-ion gas lasers, but were still tooinefficient, large, expensive, fragile for broad deployment outside ofspecialty scientific and medical applications. Additionally, the gaincrystal used in the solid state lasers typically had energy storageproperties which made the lasers difficult to modulate at high speedswhich limited its broader deployment.

To improve the efficiency of these visible lasers, high power diode (orsemiconductor) lasers were utilized. These “diode pumped solid statelasers with SHG” (DPSS with SHG) had 3 stages: electricity powers 808 nmdiode laser, 808 nm excites gain crystal, which lases at 1064 nm, 1064nm goes into frequency conversion crystal which converts to visible 532nm. The DPSS laser technology extended the life and improved the wallplug efficiency of the LPSS lasers to 5-10%, and furthercommercialization ensued into more high-end specialty industrial,medical, and scientific applications. However, the change to diodepumping increased the system cost and required precise temperaturecontrols, leaving the laser with substantial size, power consumptionwhile not addressing the energy storage properties which made the lasersdifficult to modulate at high speeds.

As high power laser diodes evolved and new specialty SHG crystals weredeveloped, it became possible to directly convert the output of theinfrared diode laser to produce blue and green laser light output. These“directly doubled diode lasers” or SHG diode lasers had 2 stages:electricity powers 1064 nm semiconductor laser, 1064 nm goes intofrequency conversion crystal which converts to visible 532 nm greenlight. These lasers designs are meant to improve the efficiency, costand size compared to DPSS-SHG lasers, but the specialty diodes andcrystals required make this challenging today. Additionally, while thediode-SHG lasers have the benefit of being directly modulate-able, theysuffer from severe sensitivity to temperature which limits theirapplication. Currently the only viable direct blue and green laser diodestructures are fabricated from the wurtzite AlGaInN material system. Themanufacturing of light emitting diodes from GaN related materials isdominated by the heteroeptiaxial growth of GaN on foreign substratessuch as Si, SiC and sapphire. Laser diode devices operate at such highcurrent densities that the crystalline defects associated withheteroepitaxial growth are not acceptable in laser diode devices due tothe high operational current densities found in laser diodes. Because ofthis, very low defect-density, free-standing GaN substrates have becomethe substrate of choice for GaN laser diode manufacturing.Unfortunately, such substrates are costly and inefficient.

SUMMARY

The invention provides a method for fabricating semiconductor laserdiodes. Typically these devices are fabricated using an epitaxialdeposition, followed by processing steps on the epitaxial substrate andoverlying epitaxial material. What follows is a general description ofthe typical configuration and fabrication of these devices.

In an example, the present invention provides a method for manufacturinga gallium and nitrogen containing laser diode device. The methodincludes providing a gallium and nitrogen containing substrate having asurface region and forming epitaxial material overlying the surfaceregion, the epitaxial material comprising an n-type cladding region, anactive region comprising of at least one active layer overlying then-type cladding region, and a p-type cladding region overlying theactive layer region. The method includes patterning the epitaxialmaterial to form a plurality of dice, each of the dice corresponding toat least one laser device, characterized by a first pitch between a pairof dice, the first pitch being less than a design width. As used herein,the design with corresponds to an actual width or design parameter of aresulting laser diode device including active regions, contacts, andinterconnects in an example, although there can be variations. Themethod includes transferring each of the plurality of dice to a carrierwafer such that each pair of dice is configured with a second pitchbetween each pair of dice, the second pitch being larger than the firstpitch corresponding to the design width.

In an example, the design width can be the actual pitch of the resultinglaser diode device with interconnects and contacts or another parameterrelated to the resulting laser diode device, which is larger than thepitch of the first pitch. As used herein the term “first” and “second”should not imply any order and should be broadly construed. Of course,there can be variations.

The present invention achieves these benefits and others in the contextof known process technology. However, a further understanding of thenature and advantages of the present invention may be realized byreference to the latter portions of the specification and attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified illustration of a laser diode according to anexample of the present invention.

FIG. 2 is a simplified illustration of a die expanded laser diodeaccording to an example of the present invention.

FIG. 3 is a schematic diagram of semipolar laser diode with the cavityaligned in the projection of c-direction with cleaved or etched mirrorsin an example.

FIG. 4 is a schematic cross-section of ridge laser diode in an example.

FIG. 5 is a top view of a selective area bonding process in an example.

FIG. 6 is a simplified process flow for epitaxial preparation in anexample.

FIG. 7 is a simplified side view illustration of selective area bondingin an example.

FIG. 8 is a simplified process flow of epitaxial preparation with activeregion protection in an example.

FIG. 9 is a simplified process flow of epitaxial preparation with activeregion protection and with ridge formation before bonding in an example.

FIG. 10 is a simplified illustration of anchored PEC undercut (top-view)in an example.

FIG. 11 is a simplified illustration of anchored PEC undercut(side-view) in an example.

DETAILED DESCRIPTION

The invention provides a method for fabricating semiconductor laserdiodes. Typically these devices are fabricated using an epitaxialdeposition, followed by processing steps on the epitaxial substrate andoverlying epitaxial material. What follows is a general description ofthe typical configuration and fabrication of these devices.

Reference can be made to the following description of the drawings, asprovided below.

Referring to FIG. 1 is a side view illustration of a state of the artGaN based laser diode after processing. Laser diodes are fabricated onthe original gallium and nitrogen containing epitaxial substrate 100,typically with epitaxial n-GaN and n-side cladding layers 101, activeregion 102, p-GaN and p-side cladding 103, insulating layers 104 andcontact/pad layers 105. Laser die pitch is labeled. All epitaxy materialnot directly under the laser ridge is wasted in this device design. Inan example, n-type cladding which may be comprised of GaN, AlGaN, orInAlGaN.

Referring now to FIG. 2 is a side view illustrations of gallium andnitrogen containing epitaxial wafer 100 before the die expansion processand carrier wafer 106 after the die expansion process. This figuredemonstrates a roughly five times expansion and thus five timesimprovement in the number of laser diodes, which can be fabricated froma single gallium and nitrogen containing substrate and overlyingepitaxial material. In this example, laser ridges (or laser diodecavities) 110 are formed after transfer of the die to the carrier wafer106. Typical epitaxial and processing layers are included for examplepurposes and are n-GaN and n-side cladding layers 101, active region102, p-GaN and p-side cladding 103, insulating layers 104, andcontact/pad layers 105. Additionally, a sacrificial region 107 andbonding material 108 are used during the die expansion process.

FIG. 3 is a schematic diagram of semipolar laser diode with the cavityaligned in the projection of c-direction with cleaved or etched mirrors.This figure provides an example of a ridge type laser diode fabricatedon a semipolar substrate and shows a cavity architecture and mirrors.FIG. 3 shows a simplified schematic diagram of semipolar laser diodewith the cavity aligned in the projection of c-direction with cleaved oretched mirrors. The laser stripe region is characterized by a cavityorientation substantially in a projection of a c-direction, which issubstantially normal to an a-direction. The laser strip region has afirst end 107 and a second end 109 and is formed on a projection of ac-direction on a {20-21} gallium and nitrogen containing substratehaving a pair of cleaved or etched mirror structures (or laser diodemirrors), which face each other.

FIG. 4 is a Schematic cross-section of ridge laser diode in an example,and shows a simplified schematic cross-sectional diagram illustrating astate of the art laser diode structure. This figure provides an exampleof a cross-section of a ridge type laser diode and shows variousfeatures associated with the device. This diagram is merely an example,which should not unduly limit the scope of the claims herein. As shown,the laser device includes gallium nitride substrate 203, which has anunderlying n-type metal back contact region 201. In an embodiment, themetal back contact region is made of a suitable material such as thosenoted below and others. In an embodiment, the device also has anoverlying n-type gallium nitride layer 205, an active region 207, and anoverlying p-type gallium nitride layer structured as a laser striperegion 211. Additionally, the device also includes an n-side separateconfinement hetereostructure (SCH), p-side guiding layer or SCH, p-AlGaNEBL, among other features. In an embodiment, the device also has a p++type gallium nitride material 213 to form a contact region.

FIG. 5 is a simplified view of a top view of a selective area bondingprocess and illustrates a die expansion process via selective areabonding. The original gallium and nitrogen containing epitaxial wafer201 has had individual die of epitaxial material and release layersdefined through processing. Individual epitaxial material die arelabeled 202 and are spaced at pitch 1. A round carrier wafer 200 hasbeen prepared with patterned bonding pads 203. These bonding pads arespaced at pitch 2, which is an even multiple of pitch 1 such thatselected sets of epitaxial die can be bonded in each iteration of theselective area bonding process. The selective area bonding processiterations continue until all epitaxial die have been transferred to thecarrier wafer 204. The gallium and nitrogen containing epitaxy substrate201 can now optionally be prepared for reuse.

In an example, FIG. 6 is a simplified diagram of process flow forepitaxial preparation including a side view illustration of an exampleepitaxy preparation process flow for the die expansion process. Thegallium and nitrogen containing epitaxy substrate 100 and overlyingepitaxial material are defined into individual die, bonding material 108is deposited, and sacrificial regions 107 are undercut. Typicalepitaxial layers are included for example purposes and are n-GaN andn-side cladding layers 101, active region 102, and p-GaN and p-sidecladding 103.

In an example, FIG. 7 is a simplified illustration of a side view of aselective area bonding process in an example. Prepared gallium andnitrogen containing epitaxial wafer 100 and prepared carrier wafer 106are the starting components of this process. The first selective areabonding iteration transfers a fraction of the epitaxial die, withadditional iterations repeated as needed to transfer all epitaxial die.Once the die expansion process is completed, state of the art laserprocessing can continue on the carrier wafer. Typical epitaxial andprocessing layers are included for example purposes and are n-GaN andn-side cladding layers 101, active region 102, p-GaN and p-side cladding103, insulating layers 104 and contact/pad layers 105. Additionally, asacrificial region 107 and bonding material 108 are used during the dieexpansion process.

In an example, FIG. 8 is a simplified diagram of an epitaxy preparationprocess with active region protection. As shown is a side viewillustration of an alternative epitaxial wafer preparation process flowduring which sidewall passivation is used to protect the active regionduring any PEC undercut etch steps. This process flow allows for a widerselection of sacrificial region materials and compositions. Typicalsubstrate, epitaxial, and processing layers are included for examplepurposes and are the gallium and nitrogen containing substrate 100,n-GaN and n-side cladding layers 101, active region 102, p-GaN andp-side cladding 103, insulating layers 104 and contact/pad layers 105.Additionally, a sacrificial region 107 and bonding material 108 are usedduring the die expansion process. FIG. 8 also shows a release region 807composed of a material from sacrificial region 107 with a smallerbandgap than an adjacent epitaxial material, wherein a lateral width ofthe release region 807 is narrower than a lateral width of immediatelyadjacent layers 801 above and below the release region 807 to formundercut regions 809 bounding each side of the release region. Further,a passivation region 804, made from insulating layer 104, extends alongsidewalls of the active region 802.

In an example, FIG. 9 is a simplified diagram of epitaxy preparationprocess flow with active region protection and ridge formation beforebonding. As shown is a side view illustration of an alternativeepitaxial wafer preparation process flow during which sidewallpassivation is used to protect the active region during any PEC undercutetch steps and laser ridges are defined on the denser epitaxial waferbefore transfer. This process flow potentially allows cost saving byperforming additional processing steps on the denser epitaxial wafer.Typical substrate, epitaxial, and processing layers are included forexample purposes and are the gallium and nitrogen containing substrate100, n-GaN and n-side cladding layers 101, active region 102, p-GaN andp-side cladding 103, insulating layers 104 and contact/pad layers 105.Additionally, a sacrificial region 107 and bonding material 108 are usedduring the die expansion process.

FIG. 10 is a simplified example of anchored PEC undercut (top-view). Asshown is a top view of an alternative release process during theselective area bonding. In this embodiment a top down etch is used toetch away the area 300, followed by the deposition of bonding metal 303.A PEC etch is then used to undercut the region 301. The sacrificialregion 302 remains intact and serves as a mechanical support during theselective area bonding process.

FIG. 11 is a simplified view of anchored PEC undercut (side-view) in anexample. As shown is a side view illustration of the anchored PECundercut. Posts of sacrificial region are included at each end of theepitaxial die for mechanical support until the bonding process iscompleted. After bonding the epitaxial material will cleave at theunsupported thin film region between the bond pads and intactsacrificial regions, enabling the selective are bonding process. Typicalepitaxial and processing layers are included for example purposes andare n-GaN and n-side cladding layers 101, active region 102, p-GaN andp-side cladding 103, insulating layers 104 and contact/pad layers 105.Additionally, a sacrificial region 107 and bonding material 108 are usedduring the die expansion process. Epitaxial material is transferred fromthe gallium and nitrogen containing epitaxial wafer 100 to the carrierwafer 106. Further details of the present method and structures can befound more particularly below.

As further background for the reader, gallium nitride, and relatedcrystals, are difficult to produce in bulk form. Growth technologiescapable of producing large area boules of GaN are still in theirinfancy, and costs for all orientations are significantly more expensivethan similar wafer sizes of other semiconductor substrates such as Si,GaAs, and InP. While large area, free-standing GaN substrates (e.g. withdiameters of two inches or greater) are available commercially, theavailability of large area non-polar and semi-polar GaN susbtrates isquite restricted. Typically, these orientations are produced by thegrowth of a c-plane oriented bool, which is then sliced into rectangularwafers at some steep angle relative to the c-plane. The width of thesewafers is limited by the thickness of the c-plane oriented boule, whichin turn is restricted by the method of boule production (e.g. typicallyhydride vapor phase epitaxy (HVPE) on a foreign substrate). Such smallwafer sizes are limiting in several respects. The first is thatepitaxial growth must be carried out on such a small wafer, whichincreases the area fraction of the wafer that is unusable due tonon-uniformity in growth near the wafer edge. The second is that afterepitaxial growth of optoelectronic device layers on a substrate, thesame number of processing steps are required on the small wafers tofabricate the final device as one would use on a large area wafer. Bothof these effects drive up the cost of manufacturing devices on suchsmall wafers, as both the cost per device fabricated and the fraction ofwafer area that is unusable increases with decreasing wafer size. Therelative immaturity of bulk GaN growth techniques additionally limitsthe total number of substrates which can be produced, potentiallylimiting the feasibility scaling up a non-polar or semi-polar GaNsubstrate based device.

Given the high cost of all orientations of GaN substrates, thedifficulty in scaling up wafer size, the inefficiencies inherent in theprocessing of small wafers, and potential supply limitations onsemi-polar and nonpolar wafers, it becomes extremely desirable tomaximize utilization of substrates and epitaxial material. In thefabrication of lateral cavity laser diodes, it is typically the casethat minimum die length is determined by the laser cavity length, butthe minimum die width is determined by other device components such aswire bonding pads or considerations such as mechanical area for diehandling in die attach processes. That is, while the laser cavity lengthlimits the laser die length, the laser die width is typically muchlarger than the laser cavity width. Since the GaN substrate andepitaxial material are only critical in and near the laser cavity regionthis presents a great opportunity to invent novel methods to form onlythe laser cavity region out of these relatively expensive materials andform the bond pad and mechanical structure of the chip from a lower costmaterial. Typical dimensions for laser cavity widths are 1-30 μm, whilewire bonding pads are ˜100 μm wide. This means that if the wire bondingpad width restriction and mechanical handling considerations wereeliminated from the GaN chip dimension between >3 and 100 times morelaser diode die could be fabricated from a single epitaxial gallium andnitrogen containing wafer. This translates to a >3 to 100 timesreduction in epitaxy and substrate costs. In conventional devicedesigns, the relatively large bonding pads are mechanically supported bythe epitaxy wafer, although they make no use of the material propertiesof the semiconductor beyond structural support.

In an example, the present invention is a method of maximizing thenumber of GaN laser devices which can be fabricated from a givenepitaxial area on a gallium and nitrogen containing substrate byspreading out the epitaxial material on a carrier wafer such that thewire bonding pads or other structural elements are mechanicallysupported by relatively inexpensive carrier wafer, while the lightemitting regions remain fabricated from the necessary epitaxialmaterial. This invention will drastically reduce the chip cost in allgallium and nitrogen based laser diodes, and in particular could enablecost efficient nonpolar and semipolar laser diode technology.

These devices include a gallium and nitrogen containing substrate (e.g.,GaN) comprising a surface region oriented in either a semipolar ornon-polar configuration, but can be others. The device also has agallium and nitrogen containing material comprising InGaN overlying thesurface region. In a specific embodiment, the present laser device canbe employed in either a semipolar or non-polar gallium containingsubstrate, as described below. As used herein, the term “substrate” canmean the bulk substrate or can include overlying growth structures suchas a gallium and nitrogen containing epitaxial region, or functionalregions such as n-type GaN, combinations, and the like. We have alsoexplored epitaxial growth and cleave properties on semipolar crystalplanes oriented between the nonpolar m-plane and the polar c-plane. Inparticular, we have grown on the {30-31} and {20-21} families of crystalplanes. We have achieved promising epitaxy structures and cleaves thatwill create a path to efficient laser diodes operating at wavelengthsfrom about 400 nm to green, e.g., 500 nm to 540 nm. These resultsinclude bright blue epitaxy in the 450 nm range, bright green epitaxy inthe 520 nm range, and smooth cleave planes orthogonal to the projectionof the c-direction.

In a specific embodiment, the gallium nitride substrate member is a bulkGaN substrate characterized by having a semipolar or non-polarcrystalline surface region, but can be others. In a specific embodiment,the bulk nitride GaN substrate comprises nitrogen and has a surfacedislocation density between about 10E5 cm⁻² and about 10E7 cm⁻² or below10E5 cm⁻². The nitride crystal or wafer may compriseAl_(x)In_(y)Ga_(1-x-y)N, where 0≤x, y, x+y≤1. In one specificembodiment, the nitride crystal comprises GaN. In one or moreembodiments, the GaN substrate has threading dislocations, at aconcentration between about 10E5 cm⁻² and about 10E8 cm⁻², in adirection that is substantially orthogonal or oblique with respect tothe surface. As a consequence of the orthogonal or oblique orientationof the dislocations, the surface dislocation density is between about10E5 cm⁻² and about 10E7 cm⁻² or below about 10E5 cm⁻². In a specificembodiment, the device can be fabricated on a slightly off-cut semipolarsubstrate as described in U.S. Ser. No. 12/749,466 filed Mar. 29, 2010,which claims priority to U.S. Provisional No. 61/164,409 filed Mar. 28,2009, commonly assigned, and hereby incorporated by reference herein.

The substrate typically is provided with one or more of the followingepitaxially grown elements, but is not limiting:

-   -   an n-GaN cladding region with a thickness of 50 nm to about 6000        nm with a Si or oxygen doping level of about 5E16 cm⁻³ to 1E19        cm⁻³    -   an InGaN region of a high indium content and/or thick InGaN        layer(s) or Super SCH region;    -   a higher bandgap strain control region overlying the InGaN        region;    -   optionally, an SCH region overlying the InGaN region;    -   multiple quantum well active region layers comprised of three to        five or four to six 3.0-5.5.0 nm InGaN quantum wells separated        by 1.5-10.0 nm GaN barriers    -   optionally, a p-side SCH layer comprised of InGaN with molar a        fraction of indium of between 1% and 10% and a thickness from 15        nm to 100 nm    -   an electron blocking layer comprised of AlGaN with molar        fraction of aluminum of between 5% and 20% and thickness from 10        nm to 15 nm and doped with Mg.    -   a p-GaN cladding layer with a thickness from 400 nm to 1000 nm        with Mg doping level of 5E17 cm⁻³ to 1E19 cm⁻³    -   a p++-GaN contact layer with a thickness from 20 nm to 40 nm        with Mg doping level of 1E20 cm⁻³ to 1E21 cm⁻³

Typically each of these regions is formed using at least an epitaxialdeposition technique of metal organic chemical vapor deposition (MOCVD),molecular beam epitaxy (MBE), or other epitaxial growth techniquessuitable for GaN growth. The active region can include one to twentyquantum well regions according to one or more embodiments. As an examplefollowing deposition of the n-type Al_(u)In_(v)Ga_(1-u-v)N layer for apredetermined period of time, so as to achieve a predeterminedthickness, an active layer is deposited. The active layer may comprise asingle quantum well or a multiple quantum well, with 2-10 quantum wells.The quantum wells may comprise InGaN wells and GaN barrier layers. Inother embodiments, the well layers and barrier layers compriseAl_(w)In_(x)Ga_(1-w-x)N and Al_(y)In_(z)Ga_(1-y-z)N, respectively, where0≤w, x, y, z, w+x, y+z≤1, where w<u, y and/or x>v, z so that the bandgapof the well layer(s) is less than that of the barrier layer(s) and then-type layer. The well layers and barrier layers may each have athickness between about 1 nm and about 15 nm. In another embodiment, theactive layer comprises a double heterostructure, with an InGaN orAlwInxGa1-w-xN layer about 10 nm to 100 nm thick surrounded by GaN orAl_(y)In_(z)Ga_(1-y-z)N layers, where w<u, y and/or x>v, z. Thecomposition and structure of the active layer are chosen to providelight emission at a preselected wavelength. The active layer may be leftundoped (or unintentionally doped) or may be doped n-type or p-type.

The active region can also include an electron blocking region, and aseparate confinement heterostructure. In some embodiments, an electronblocking layer is preferably deposited. The electron-blocking layer maycomprise Al_(s)In_(t)Ga_(1-s-t)N, where 0≤s, t, s+t≤1, with a higherbandgap than the active layer, and may be doped p-type or the electronblocking layer comprises an AlGaN/GaN super-lattice structure,comprising alternating layers of AlGaN and GaN. Alternatively, there maybe no electron blocking layer. As noted, the p-type gallium nitridestructure, is deposited above the electron blocking layer and activelayer(s). The p-type layer may be doped with Mg, to a level betweenabout 10E16 cm-3 and 10E22 cm-3, and may have a thickness between about5 nm and about 1000 nm. The outermost 1-50 nm of the p-type layer may bedoped more heavily than the rest of the layer, so as to enable animproved electrical contact.

The present invention is directed towards the fabrication ofoptoelectronic devices from semiconductor wafers. In particular, thepresent invention increases utilization of substrate wafers and epitaxymaterial through a selective area bonding process to transfer individualdie of epitaxy material to a carrier wafer in such a way that the diepitch is increased on the carrier wafer relative to the original epitaxywafer. The arrangement of epitaxy material allows device componentswhich do not require the presence of the expensive gallium and nitrogencontaining substrate and overlying epitaxy material often fabricated ona gallium and nitrogen containing substrate to be fabricated on thelower cost carrier wafer, allowing for more efficient utilization of thegallium and nitrogen containing substrate and overlying epitaxymaterial.

In an embodiment, mesas of gallium and nitrogen containing laser diodeepitaxy material are fabricated in a dense array on a gallium andnitrogen containing substrate. This pattern pitch will be referred to asthe ‘first pitch’. The first pitch is often a design width that issuitable for fabricating each of the epitaxial regions on the substrate,while not large enough for completed laser devices, which often desirelarger non-active regions or regions for contacts and the like. Forexample, these mesas would have a first pitch ranging from about 5microns to about 30 microns or to about 50 microns. Each of these mesasis a ‘die’.

In an example, these die are then transferred to a carrier wafer at asecond pitch such that the second pitch on the carrier wafer is greaterthan the first pitch on the gallium and nitrogen containing substrate.In an example, the second pitch is configured with the die to allow eachdie with a portion of the carrier wafer to be a laser device, includingcontacts and other components. For example, the second pitch would beabout 100 microns to about 200 microns or to about 300 microns. Thesecond die pitch allows for easy mechanical handling and room for wirebonding pads positioned in the regions of carrier wafer in-betweenepitaxy mesas, enabling a greater number of laser diodes to befabricated from a given gallium and nitrogen containing substrate andoverlying epitaxy material. Side view schematics of state of the art anddie expanded laser diodes are shown in FIG. 1 and FIG. 2. Typicaldimensions for laser ridge widths and the widths necessary formechanical and wire bonding considerations are from 1 μm to 30 μm andfrom 100 μm to 300 μm, respectively, allowing for large potentialimprovements in gallium and nitrogen containing substrate and overlyingepitaxy material usage efficiency with the current invention.

FIG. 4 is a simplified schematic cross-sectional diagram illustrating astate of the art laser diode structure. This diagram is merely anexample, which should not unduly limit the scope of the claims herein.One of ordinary skill in the art would recognize other variations,modifications, and alternatives. As shown, the laser device includesgallium nitride substrate 203, which has an underlying n-type metal backcontact region 201. In an embodiment, the metal back contact region ismade of a suitable material such as those noted below and others.Further details of the contact region can be found throughout thepresent specification and more particularly below.

In an embodiment, the device also has an overlying n-type galliumnitride layer 205, an active region 207, and an overlying p-type galliumnitride layer structured as a laser stripe region 211. Additionally, thedevice also includes an n-side separate confinement hetereostructure(SCH) 206, p-side guiding layer or SCH 208, p-AlGaN EBL 209, among otherfeatures. In an embodiment, the device also has a p++ type galliumnitride material 213 to form a contact region. In an embodiment, the p++type contact region has a suitable thickness and may range from about 10nm 50 nm, or other thicknesses. In an embodiment, the doping level canbe higher than the p-type cladding region and/or bulk region. In anembodiment, the p++ type region has doping concentration ranging fromabout 10¹⁹ to 10²¹ Mg/cm³, and others. The p++ type region preferablycauses tunneling between the semiconductor region and overlying metalcontact region. In an embodiment, each of these regions is formed usingat least an epitaxial deposition technique of metal organic chemicalvapor deposition (MOCVD), molecular beam epitaxy (MBE), or otherepitaxial growth techniques suitable for GaN growth. In an embodiment,the epitaxial layer is a high quality epitaxial layer overlying then-type gallium nitride layer. In some embodiments the high quality layeris doped, for example, with Si or O to form n-type material, with adopant concentration between about 10¹⁶ cm⁻³ and 10²⁰ cm⁻³.

The device has a laser stripe region formed overlying a portion of theoff-cut crystalline orientation surface region. As example, FIG. 3 is asimplified schematic diagram of semipolar laser diode with the cavityaligned in the projection of c-direction with cleaved or etched mirrors.The laser stripe region is characterized by a cavity orientationsubstantially in a projection of a c-direction, which is substantiallynormal to an a-direction. The laser strip region has a first end 107 anda second end 109 and is formed on a projection of a c-direction on a{20-21} gallium and nitrogen containing substrate having a pair ofcleaved mirror structures, which face each other. The first cleavedfacet comprises a reflective coating and the second cleaved facetcomprises no coating, an antireflective coating, or exposes gallium andnitrogen containing material. The first cleaved facet is substantiallyparallel with the second cleaved facet. The first and second cleavedfacets are provided by a scribing and breaking process according to anembodiment or alternatively by etching techniques using etchingtechnologies such as reactive ion etching (ME), inductively coupledplasma etching (ICP), or chemical assisted ion beam etching (CAIBE), orother method. The first and second mirror surfaces each comprise areflective coating. The coating is selected from silicon dioxide,hafnia, and titania, tantalum pentoxide, zirconia, includingcombinations, and the like. Depending upon the design, the mirrorsurfaces can also comprise an anti-reflective coating.

In a specific embodiment, the method of facet formation includessubjecting the substrates to a laser for pattern formation. In apreferred embodiment, the pattern is configured for the formation of apair of facets for one or more ridge lasers. In a preferred embodiment,the pair of facets face each other and are in parallel alignment witheach other. In a preferred embodiment, the method uses a UV (355 nm)laser to scribe the laser bars. In a specific embodiment, the laser isconfigured on a system, which allows for accurate scribe linesconfigured in one or more different patterns and profiles. In one ormore embodiments, the laser scribing can be performed on the back-side,front-side, or both depending upon the application. Of course, there canbe other variations, modifications, and alternatives.

In a specific embodiment, the method uses backside laser scribing or thelike. With backside laser scribing, the method preferably forms acontinuous line laser scribe that is perpendicular to the laser bars onthe backside of the GaN substrate. In a specific embodiment, the laserscribe is generally 15-20 um deep or other suitable depth. Preferably,backside scribing can be advantageous. That is, the laser scribe processdoes not depend on the pitch of the laser bars or other like pattern.Accordingly, backside laser scribing can lead to a higher density oflaser bars on each substrate according to a preferred embodiment. In aspecific embodiment, backside laser scribing, however, may lead toresidue from the tape on one or more of the facets. In a specificembodiment, backside laser scribe often requires that the substratesface down on the tape. With front-side laser scribing, the backside ofthe substrate is in contact with the tape. Of course, there can be othervariations, modifications, and alternatives.

Laser scribe Pattern: The pitch of the laser mask is about 200 um, butcan be others. The method uses a 170 um scribe with a 30 um dash for the200 um pitch. In a preferred embodiment, the scribe length is maximizedor increased while maintaining the heat affected zone of the laser awayfrom the laser ridge, which is sensitive to heat.

Laser scribe Profile: A saw tooth profile generally produces minimalfacet roughness. It is believed that the saw tooth profile shape createsa very high stress concentration in the material, which causes thecleave to propagate much easier and/or more efficiently.

In a specific embodiment, the method of facet formation includessubjecting the substrates to mechanical scribing for pattern formation.In a preferred embodiment, the pattern is configured for the formationof a pair of facets for one or more ridge lasers. In a preferredembodiment, the pair of facets face each other and are in parallelalignment with each other. In a preferred embodiment, the method uses adiamond tipped scribe to physically scribe the laser bars, though aswould be obvious to anyone learned in the art a scribe tipped with anymaterial harder than GaN would be adequate. In a specific embodiment,the laser is configured on a system, which allows for accurate scribelines configured in one or more different patterns and profiles. In oneor more embodiments, the mechanical scribing can be performed on theback-side, front-side, or both depending upon the application. Ofcourse, there can be other variations, modifications, and alternatives.

In a specific embodiment, the method uses backside scribing or the like.With backside mechanical scribing, the method preferably forms acontinuous line scribe that is perpendicular to the laser bars on thebackside of the GaN substrate. In a specific embodiment, the laserscribe is generally 15-20 um deep or other suitable depth. Preferably,backside scribing can be advantageous. That is, the mechanical scribeprocess does not depend on the pitch of the laser bars or other likepattern. Accordingly, backside scribing can lead to a higher density oflaser bars on each substrate according to a preferred embodiment. In aspecific embodiment, backside mechanical scribing, however, may lead toresidue from the tape on one or more of the facets. In a specificembodiment, backside mechanical scribe often requires that thesubstrates face down on the tape. With front-side mechanical scribing,the backside of the substrate is in contact with the tape. Of course,there can be other variations, modifications, and alternatives.

It is well known that etch techniques such as chemical assisted ion beametching (CAIBE), inductively coupled plasma (ICP) etching, or reactiveion etching (RIE) can result in smooth and vertical etched sidewallregions, which could serve as facets in etched facet laser diodes. Inthe etched facet process a masking layer is deposited and patterned onthe surface of the wafer. The etch mask layer could be comprised ofdielectrics such as silicon dioxide (SiO2), silicon nitride (SixNy), acombination thereof or other dielectric materials. Further, the masklayer could be comprised of metal layers such as Ni or Cr, but could becomprised of metal combination stacks or stacks comprising metal anddielectrics. In another approach, photoresist masks can be used eitheralone or in combination with dielectrics and/or metals. The etch masklayer is patterned using conventional photolithography and etch steps.The alignment lithography could be performed with a contact aligner orstepper aligner. Such lithographically defined mirrors provide a highlevel of control to the design engineer. After patterning of thephotoresist mask on top of the etch mask is complete, the patterns inthen transferred to the etch mask using a wet etch or dry etchtechnique. Finally, the facet pattern is then etched into the waferusing a dry etching technique selected from CAIBE, ICP, RIE and/or othertechniques. The etched facet surfaces must be highly vertical of betweenabout 87 and 93 degrees or between about 89 and 91 degrees from thesurface plane of the wafer. The etched facet surface region must be verysmooth with root mean square roughness values of less than 50 nm, 20 nm,5 nm, or 1 nm. Lastly, the etched must be substantially free fromdamage, which could act as nonradiative recombination centers and hencereduce the COMD threshold. CAIBE is known to provide very smooth and lowdamage sidewalls due to the chemical nature of the etch, while it canprovide highly vertical etches due to the ability to tilt the waferstage to compensate for any inherent angle in etch.

The laser stripe is characterized by a length and width. The lengthranges from about 50 microns to about 3000 microns, but is preferablybetween 10 microns and 400 microns, between about 400 microns and 800microns, or about 800 microns and 1600 microns, but could be others. Thestripe also has a width ranging from about 0.5 microns to about 50microns, but is preferably between 0.8 microns and 2.5 microns forsingle lateral mode operation or between 2.5 um and 35 um formulti-lateral mode operation, but can be other dimensions. In a specificembodiment, the present device has a width ranging from about 0.5microns to about 1.5 microns, a width ranging from about 1.5 microns toabout 3.0 microns, a width ranging from 3.0 microns to about 35 microns,and others. In a specific embodiment, the width is substantiallyconstant in dimension, although there may be slight variations. Thewidth and length are often formed using a masking and etching process,which are commonly used in the art.

The laser stripe is provided by an etching process selected from dryetching or wet etching. The device also has an overlying dielectricregion, which exposes a p-type contact region. Overlying the contactregion is a contact material, which may be metal or a conductive oxideor a combination thereof. The p-type electrical contact may be depositedby thermal evaporation, electron beam evaporation, electroplating,sputtering, or another suitable technique. Overlying the polished regionof the substrate is a second contact material, which may be metal or aconductive oxide or a combination thereof and which comprises the n-typeelectrical contact. The n-type electrical contact may be deposited bythermal evaporation, electron beam evaporation, electroplating,sputtering, or another suitable technique.

Given the high gallium and nitrogen containing substrate costs,difficulty in scaling up gallium and nitrogen containing substrate size,the inefficiencies inherent in the processing of small wafers, andpotential supply limitations on polar, semi-polar, and nonpolar galliumand nitrogen containing wafers, it becomes extremely desirable tomaximize utilization of available gallium and nitrogen containingsubstrate and overlying epitaxial material. In the fabrication oflateral cavity laser diodes, it is typically the case that minimum diesize is determined by device components such as the wire bonding pads ormechanical handling considerations, rather than by laser cavity widths.Minimizing die size is critical to reducing manufacturing costs assmaller die sizes allow a greater number of devices to be fabricated ona single wafer in a single processing run. The current invention is amethod of maximizing the number of devices which can be fabricated froma given gallium and nitrogen containing substrate and overlyingepitaxial material by spreading out the epitaxial material onto acarrier wafer via a die expansion process.

A top down view of one preferred embodiment of the die expansion processis depicted in FIG. 5. The starting materials are patterned epitaxy andcarrier wafers. Herein, the ‘epitaxy wafer’ or ‘epitaxial wafer’ isdefined as the original gallium and nitrogen containing wafer on whichthe epitaxial material making up the active region was grown, while the‘carrier wafer’ is defined as a wafer to which epitaxial layers aretransferred for convenience of processing. The carrier wafer can bechosen based on any number of criteria including but not limited tocost, thermal conductivity, thermal expansion coefficients, size,electrical conductivity, optical properties, and processingcompatibility. The patterned epitaxy wafer is prepared in such a way asto allow subsequent selective release of bonded epitaxy regions. Thepatterned carrier wafer is prepared such that bond pads are arranged inorder to enable the selective area bonding process. These wafers can beprepared by a variety of process flows, some embodiments of which aredescribed below. In the first selective area bond step, the epitaxywafer is aligned with the pre-patterned bonding pads on the carrierwafer and a combination of pressure, heat, and/or sonication is used tobond the mesas to the bonding pads. The bonding material can be avariety of media including but not limited to metals, polymers, waxes,and oxides. Only epitaxial die which are in contact with a bond bad onthe carrier wafer will bond. Sub-micron alignment tolerances arepossible on commercial die bonders. The epitaxy wafer is then pulledaway, breaking the epitaxy material at a weakened epitaxial releaselayer such that the desired epitaxial layers remain on the carrierwafer. Herein, a ‘selective area bonding step’ is defined as a singleiteration of this process. In the example depicted in FIG. 5, onequarter of the epitaxial die are transferred in this first selectivebond step, leaving three quarters on the epitaxy wafer. The selectivearea bonding step is then repeated to transfer the second quarter, thirdquarter, and fourth quarter of the epitaxial die to the patternedcarrier wafer. This selective area bond may be repeated any number oftimes and is not limited to the four steps depicted in FIG. 5. Theresult is an array of epitaxial die on the carrier wafer with a widerdie pitch than the original die pitch on the epitaxy wafer. The diepitch on the epitaxial wafer will be referred to as pitch 1, and the diepitch on the carrier wafer will be referred to as pitch 2, where pitch 2is greater than pitch 1. At this point standard laser diode processescan be carried out on the carrier wafer. Side profile views of devicesfabricated with state of the art methods and the methods described inthe current invention are depicted in FIG. 1 and FIG. 2, respectively.The device structure enabled by the current invention only contains therelatively expensive epitaxy material where the optical cavity requiresit, and has the relatively large bonding pads and/or other devicecomponents resting on a carrier wafer. Typical dimensions for laserridge widths and bonding pads are <30 μm and >100 μm, respectively,allowing for three or more times improved epitaxy usage efficiency withthe current invention.

There are many methods by which the expanded die pitch can be achieved.One embodiment for the fabrication of GaN based laser diodes is depictedin FIG. 6 and FIG. 7. This embodiment uses a bandgap selectivephoto-electrical chemical (PEC) etch to undercut an array of mesasetched into the epitaxial layers, followed by a selective area bondingprocess on a patterned carrier wafer. The preparation of the epitaxywafer is shown in FIG. 6 and the selective area bonding process is shownin FIG. 7. This process requires the inclusion of a buried sacrificialregion, which can be selectively PEC etched by bandgap. For GaN basedoptoelectronic devices, InGaN quantum wells have been shown to be aneffective sacrificial region during PEC etching.^(1,2) The first stepdepicted in FIG. 6 is a top down etch to expose the sacrificial layers,followed by a bonding metal deposition as shown in FIG. 6. With thesacrificial region exposed a bandgap selective PEC etch is used toundercut the mesas. The bandgaps of the sacrificial region and all otherlayers are chosen such that only the sacrificial region will absorblight, and therefor etch, during the PEC etch. With proper control ofetch rates a thin strip of material 107 can be left to weakly connectthe mesas to the epitaxy substrate. This wafer is then aligned andbonded to a patterned carrier wafer, as shown in FIG. 7. Gold-goldmetallic bonding is used as an example in this work, although a widevariety of oxide bonds, polymer bonds, wax bonds etc. are potentiallysuitable. Submicron alignment tolerances are possible using commercialavailable die bonding equipment. The carrier wafer is patterned in sucha way that only selected mesas come in contact with the metallic bondpads on the carrier wafer. When the epitaxy substrate is pulled away thebonded mesas break off at the weakened sacrificial region and a portion111 of the mesas remain intact on the carrier wafer, while the un-bondedmesas remain attached to the epitaxy substrate. This selective areabonding process can then be repeated to transfer the remaining mesas inthe desired configuration. This process can be repeated through anynumber of iterations and is not limited to the two iterations depictedin FIG. 7. The carrier wafer can be of any size, including but notlimited to 2 inch, 3 inch, 4 inch, 6 inch, 8 inch, and 12 inch. Afterall desired mesas have been transferred, a second bandgap selective PECetch can be optionally used to remove any remaining sacrificial regionmaterial to yield smooth surfaces. At this point standard laser diodeprocesses can be carried out on the carrier wafer.

Another embodiment of the invention uses a sacrificial region with ahigher bandgap than the active region such that both layers areabsorbing during the bandgap PEC etching process. In this embodiment,the active region can be prevented from etching during the bandgapselective PEC etch using an insulating protective layer on the sidewall,as shown in FIG. 8. The first step depicted in FIG. 8 is an etch toexpose the active region of the device. This step is followed by thedeposition of a protective insulating layer on the mesa sidewalls, whichserves to block PEC etching of the active region during the latersacrificial region undercut PEC etching step. A second top down etch isthen performed to expose the sacrificial layers and bonding metal isdeposited as shown in FIG. 8. With the sacrificial region exposed abandgap selective PEC etch is used to undercut the mesas. At this point,the selective area bonding process shown in FIG. 7 is used to continuefabricating devices.

Another embodiment of the invention incorporates the fabrication ofdevice components on the dense epitaxy wafers before the selective areabonding steps. In the embodiment depicted in FIG. 9 the laser ridge,sidewall passivation, and contact metal are fabricated on the originalepitaxial wafer before the die expansion process. This process flow isgiven for example purposes only and is not meant to limit which devicecomponents can be processed before the die expansion process. This workflow has potential cost advantages since additional steps are performedon the higher density epitaxial wafer before the die expansion process.A detailed schematic of this process flow is depicted in FIG. 9.

In another preferred embodiment of the invention the gallium andnitrogen epitaxial material will be grown on a gallium and nitrogencontaining substrate material of one of the following orientations:m-plane, {50-51}, {30-31}, {20-21}, {30-32}, {50-5-1}, {30-3-1},{20-2-1}, {30-3-2}, or offcuts of these planes within +/−5 degreestowards a-plane and/or c-plane

In another embodiment of the invention individual PEC undercut etchesare used after each selective bonding step for etching away thesacrificial release layer of only bonded mesas. Which epitaxial die getundercut is controlled by only etching down to expose the sacrificiallayer of mesas which are to be removed on the current selective bondingstep. The advantage of this embodiment is that only a very coarsecontrol of PEC etch rates is required. This comes at the cost ofadditional processing steps and geometry constrains.

In another embodiment of the invention the bonding layers can be avariety of bonding pairs including metal-metal, oxide-oxide, solderingalloys, photoresists, polymers, wax, etc.

In another embodiment of the invention the sacrificial region iscompletely removed by PEC etching and the mesa remains anchored in placeby any remaining defect pillars. PEC etching is known to leave intactmaterial around defects which act as recombination centers.^(2,3)Additional mechanisms by which a mesa could remain in place after acomplete sacrificial etch include static forces or Van der Waals forces.

In another embodiment of the invention a shaped sacrificial regionexpose mesa is etched to leave larger regions near the ends of eachepitaxy die. Bonding metal is placed only on the regions of epitaxy thatare to be transferred. A PEC etch is then performed such that theepitaxy die to be transferred is completely undercut while the largerregions near the end are only partially undercut. The intact sacrificialregions at the ends of the die provide mechanical stability through theselective area bonding step. As only a few nanometers of thickness willbe undercut, this geometry should be compatible with standard bondingprocesses. After the selective area bonding step, the epitaxy andcarrier wafers are mechanically separated, cleaving at the weak pointsbetween the bond metal and intact sacrificial regions. Exampleschematics of this process are depicted in FIGS. 10 and 11. After thedesired number of repetitions is completed, state of the art laser diodefabrication procedures can be applied to the die expanded carrier wafer.

In another embodiment of the invention, the release of the epitaxiallayers is accomplished by means other than PEC etching, such as laserlift off.

In another embodiment of the invention the carrier wafer is anothersemiconductor material, a metallic material, or a ceramic material. Somepotential candidates include silicon, gallium arsenide, sapphire,silicon carbide, diamond, gallium nitride, AlN, polycrystalline AlN,indium phosphide, germanium, quartz, copper, gold, silver, aluminum,stainless steel, or steel.

In another embodiment of the invention the laser facets are produced bycleaving processes. If a suitable carrier wafer is selected it ispossible to use the carrier wafer to define cleaving planes in theepitaxy material. This could improve the yield, quality, ease, and/oraccuracy of the cleaves.

In another embodiment of the invention the laser facets are produced byetched facet processes. In the etched facet embodiment alithographically defined mirror pattern is etched into the gallium andnitrogen to form facets. The etch process could be a dry etch processselected from inductively coupled plasma etching (ICP), chemicallyassisted ion beam etching (CAME), or reactive ion etching (RIE) Etchedfacet process can be used in combination with the die expansion processto avoid facet formation by cleaving, potentially improved yield andfacet quality.

In another embodiment of the invention die singulation is achieved bycleaving processes which are assisted by the choice of carrier wafer.For example, if a silicon or GaAs carrier wafer is selected there willbe a system of convenient cubic cleave planes available for diesingulation by cleaving. In this embodiment there is no need for thecleaves to transfer to the epitaxy material since the die singulationwill occur in the carrier wafer material regions only.

In another embodiment of the invention any of the above process flowscan be used in combination with the wafer tiling. As an example, 7.5 mmby 18 mm substrates can be tiled onto a 2 inch carrier wafer, allowingtopside processing and selective area bonding to be carried out onmultiple epitaxy substrates in parallel for further cost savings.

In another embodiment of the invention the substrate wafer is reclaimedafter the selective area bond steps through a re-planarization andsurface preparation procedure. The epitaxy wafer can be reused anypractical number of times.⁶

In an example, the present invention provides a method for increasingthe number of gallium and nitrogen containing laser diode devices whichcan be fabricated from a given epitaxial surface area; where the galliumand nitrogen containing epitaxial layers overlay gallium and nitrogencontaining substrates. The epitaxial material comprises of at least thefollowing layers: a sacrificial region which can be selectively etchedusing a bandgap selective PEC etch, an n-type cladding region, an activeregion comprising of at least one active layer overlying the n-typecladding region, and a p-type cladding region overlying the active layerregion. The gallium and nitrogen containing epitaxial material ispatterned into die with a first die pitch; the die from the gallium andnitrogen containing epitaxial material with a first pitch is transferredto a carrier wafer to form a second die pitch on the carrier wafer; thesecond die pitch is larger than the first die pitch.

In an example, each epitaxial die is an etched mesa with a pitch ofbetween 1 μm and 10 μm wide or between 10 micron and 50 microns wide andbetween 50 and 3000 μm long. In an example, the second die pitch on thecarrier wafer is between 100 microns and 200 microns or between 200microns and 300 microns. In an example, the second die pitch on thecarrier wafer is between 2 times and 50 times larger than the die pitchon the epitaxy wafer. In an example, semiconductor laser devices arefabricated on the carrier wafer after epitaxial transfer. In an example,the semiconductor devices contain GaN, AlN, InN, InGaN, AlGaN, InAlN,and/or InAlGaN. In an example, the gallium and nitrogen containingmaterial are grown on a polar, non-polar, or semi-polar plane. In anexample, one or multiple laser diode cavities are fabricated on each dieof epitaxial material. In an example, device components, which do notrequire epitaxy material are placed in the space between epitaxy die.

As used herein, the term GaN substrate is associated with GroupIII-nitride based materials including GaN, InGaN, AlGaN, or other GroupIII containing alloys or compositions that are used as startingmaterials. Such starting materials include polar GaN substrates (i.e.,substrate where the largest area surface is nominally an (h k l) planewherein h=k=0, and l is non-zero), non-polar GaN substrates (i.e.,substrate material where the largest area surface is oriented at anangle ranging from about 80-100 degrees from the polar orientationdescribed above towards an (h k l) plane wherein l=0, and at least oneof h and k is non-zero) or semi-polar GaN substrates (i.e., substratematerial where the largest area surface is oriented at an angle rangingfrom about +0.1 to 80 degrees or 110-179.9 degrees from the polarorientation described above towards an (h k l) plane wherein l=0, and atleast one of h and k is non-zero).

As shown, the present device can be enclosed in a suitable package. Suchpackage can include those such as in TO-38 and TO-56 headers. Othersuitable package designs and methods can also exist, such as TO-9 orflat packs where fiber optic coupling is required and even non-standardpackaging. In a specific embodiment, the present device can beimplemented in a co-packaging configuration.

In other embodiments, the present laser device can be configured in avariety of applications. Such applications include laser displays,metrology, communications, health care and surgery, informationtechnology, and others. As an example, the present laser device can beprovided in a laser display such as those described in U.S. Ser. No.12/789,303 filed May 27, 2010, which claims priority to U.S. ProvisionalNos. 61/182,105 filed May 29, 2009 and 61/182,106 filed May 29, 2009,each of which is hereby incorporated by reference herein.

In an example, the present techniques can be used in conjunction with“Semiconductor Laser Diode on Tiled Gallium Containing Material,” listedunder U.S. Ser. No. 14/175,622, filed Feb. 7, 2014, (Attorney Docket No.96019-899917 (100400US), commonly assigned, and hereby incorporated byreference herein. In an example, the present techniques can be used withthe tiling technique for processing small GaN wafers prior to transferof GaN epi to carrier wafer for low cost, high volume small GaN wafers.

In an alternative example, the present technique can also be used inconjunction with a double ITO and cleaving technique titled “Gallium andNitrogen Containing Laser Device Having Confinement Region,” which isdescribed in U.S. Ser. No. 61/892,981, filed Oct. 18, 2013, (AttorneyDocket No. 96019-887865 (100100US), commonly assigned, and herebyincorporated by reference herein. That is, the present technique can beintegrated with the double clad and cleaving technology.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. As an example, the packaged device can include any combination ofelements described above, as well as outside of the presentspecification. As used herein, the term “substrate” can mean the bulksubstrate or can include overlying growth structures such as a galliumand nitrogen containing epitaxial region, or functional regions such asn-type GaN, combinations, and the like. Additionally, the examplesillustrates two waveguide structures in normal configurations, there canbe variations, e.g., other angles and polarizations. For semi-polar, thepresent method and structure includes a stripe oriented perpendicular tothe c-axis, an in-plane polarized mode is not an Eigen-mode of thewaveguide. The polarization rotates to elliptic (if the crystal angle isnot exactly 45 degrees, in that special case the polarization wouldrotate but be linear, like in a half-wave plate). The polarization willof course not rotate toward the propagation direction, which has nointeraction with the A1 band. The length of the a-axis stripe determineswhich polarization comes out at the next mirror. Although theembodiments above have been described in terms of a laser diode, themethods and device structures can also be applied to any light emittingdiode device. Therefore, the above description and illustrations shouldnot be taken as limiting the scope of the present invention which isdefined by the appended claims.

REFERENCES

-   1. Holder, C., Speck, J. S., DenBaars, S. P., Nakamura, S. &    Feezell, D. Demonstration of Nonpolar GaN-Based Vertical-Cavity    Surface-Emitting Lasers. Appl. Phys. Express 5, 092104 (2012).-   2. Tamboli, A. Photoelectrochemical etching of gallium nitride for    high quality optical devices. (2009). at    <http://adsabs.harvard.edu/abs/2009PhDT . . . 68T>-   3. Yang, B. MICROMACHINING OF GaN USING PHOTOELECTROCHEMICAL    ETCHING. (2005).-   4. Sink, R. Cleaved-Facet Group-III Nitride Lasers. (2000). at    <http://siliconphotonics.ece.ucsb.edu/sites/default/files/publications/2000    Cleaved-Faced Group-III Nitride Lasers.PDF>-   5. Bowers, J., Sink, R. & Denbaars, S. Method for making cleaved    facets for lasers fabricated with gallium nitride and other noncubic    materials. U.S. Pat. No. 5,985,687 (1999). at    <http://www.google.com/patents?hl=en&lr=&vid=USPAT5985687&id=no8XAAAAEBAJ&oi=fnd&dq=Method+for+making+cleaved+facets+for+lasers+fabricated+with+gallium+nitride+and+other+noncubic+materials&printsec=abstract>-   6. Holder, C. O., Feezell, D. F., Denbaars, S. P. & Nakamura, S.    Method for the reuse of gallium nitride epitaxial substrates.    (2012).

What is claimed is:
 1. A method for manufacturing a gallium and nitrogencontaining device, the method comprising: providing a gallium andnitrogen containing substrate having a surface region; forming epitaxialmaterial overlying the surface region, the epitaxial material comprisingan n-type cladding region, an active region comprising of at least oneactive layer overlying the n-type cladding region, and a p-type claddingregion overlying the active layer region; patterning the epitaxialmaterial to form a plurality of dice, each of the dice corresponding toat least one device, characterized by a first pitch between a pair ofdice, the first pitch being less than a design width; transferring atleast a portion of the plurality of dice to a carrier wafer such thateach pair of transferred dice is configured with a second pitch betweeneach pair of dice, the second pitch being larger than the first pitchand corresponding to the design width, the transferring comprising:selectively removing at least a portion of a release region of one ormore die while leaving an anchor region intact between the one or moredie and the gallium and nitrogen containing substrate, selectivelybonding the one or more die to the carrier wafer, and releasing the oneor more die from the gallium and nitrogen containing substrate byseparating the anchor region associated with each of the one or more diewhile a portion of the epitaxial material remains bonded to the carrierwafer.
 2. The method of claim 1, wherein each die is shaped as a mesa,and each pair of die having the first pitch ranging between 1 μm and 10μm or between 10 micron and 50 microns wide or between 50 and 3000 μmlong; and the patterning comprising an etching process.
 3. The method ofclaim 1, wherein the second pitch on the carrier wafer is between 100microns and 200 microns or between 200 microns and 300 microns.
 4. Themethod of claim 1, wherein the second pitch on the carrier wafer isbetween 2 times and 50 times larger than the first pitch.
 5. The methodof claim 1, further comprising processing each of the die to form atleast one laser device on each die after the transferring or furthercomprising forming one or multiple laser diode cavities on each die ofepitaxial material.
 6. The method of claim 1, wherein each pair of diceoverlying the carrier wafer is defined by the second pitch; and furthercomprising forming one or more components overlying a space defined bythe second pitch, the one or more components being selected from acontact region or a bonding pad.
 7. The method of claim 1, wherein thecarrier wafer is characterized by a conductive material for a contactregion or contact regions; wherein each of the devices is characterizedby a wavelength ranging between 200 and 2000 nm; and wherein each of thedevice comprising a pair of facets configured from a cleaving process oran etching process, the etching process being selected from inductivelycoupled plasma etching, chemical assisted ion beam etching, or reactiveion beam etching.
 8. The method of claim 1, further comprisingsingulating each of the die by separating each pair of die at a spacedefined by the second pitch; wherein the epitaxial material containsGaN, AlN, InN, InGaN, AlGaN, InAlN, and/or InAlGaN.
 9. The method ofclaim 1, wherein the gallium and nitrogen containing material are grownon a polar, non-polar, or semi-polar plane.
 10. The method of claim 1,wherein the carrier wafer comprises at least one of silicon, galliumarsenide, sapphire, silicon carbide, diamond, gallium nitride, AlN,indium phosphide, or metallic.
 11. The method of claim 1, wherein theselectively bonding comprises bonding each of the one or more die to abonding pad on the carrier wafer.
 12. The method of claim 1, wherein thetransferring is repeated N times to transfer one or more other die tothe carrier wafer, where N is an integer between 1 and
 50. 13. Themethod of claim 1, wherein the transferring is repeated N times totransfer one or more other die to the carrier wafer, where N is aninteger between 1 and 50 to remove each of the die to be bonded to thecarrier wafer; whereupon the carrier wafer has a larger diameter than adiameter of the gallium and nitrogen containing substrate.
 14. Themethod of claim 1 wherein the transferring is repeated N times totransfer one or more other die to the carrier wafer, where N is aninteger between 1 and 50 to remove each of the die to be bonded to thecarrier wafer; whereupon the carrier wafer has a larger diameter than adiameter of the gallium and nitrogen containing substrate; whereuponbonds between each of the one or more die and the carrier wafer compriseat least one of metal-metal pairs, oxide-oxide pairs, spin-on-glass,soldering alloys, polymers, photoresists, and/or wax.
 15. The method ofclaim 1, wherein the transferring is repeated N times to transfer one ormore other die to the carrier wafer, where N is an integer between 1 and50 to remove each of the die to be bonded to the carrier wafer;whereupon the carrier wafer has a larger diameter than a diameter of thegallium and nitrogen containing substrate; whereupon bonds between eachof the one or more die and the carrier wafer comprise at least one ofmetal-metal pairs, oxide-oxide pairs, spin-on-glass, soldering alloys,polymers, photoresists, and/or wax; and wherein the selectively removinguses a bandgap selective photo-electrical-chemical (PEC) etching toremove the portion of the release region.
 16. The method of claim 1,wherein the release region is composed of a material with a smallerbandgap than an adjacent epitaxial layer.
 17. The method of claim 1,wherein the release region is composed of InGaN, InN, InAlN, or InAlGaN.18. The method of claim 15, wherein the PEC etching selectively removessubstantially all of the release region while leaving intact a portionof the release region to provide structure during the selectivelybonding, the portion of the release region forming the anchor region.19. The method of claim 15, wherein the PEC etching selectively removesthe release region while leaving the anchor region in tact to supportthe die during the selective bonding.
 20. The method of claim 15,wherein the PEC etching selectively removes the release region whileleaving the anchor region intact to support the die during the selectivebonding, the anchor region comprising a defect pillar, a static force,or a Van der Waals force.
 21. The method of claim 15 further comprisingan additional PEC etching process to completely remove remainingportions of the release region on the one or more die while the one ormore die are bonded to the carrier wafer.
 22. The method of claim 15further comprising forming a metal material overlying the one or moredie before transferring, while leaving exposed one or more anchorregions, which are configured to selectively break and separate fromeach of the die after selectively bonding.
 23. The method of claim 1wherein the selectively removing forms an undercut region within avicinity of each of the one or more die to enable selective release ofeach of the one or more die.
 24. The method of claim 15 wherein each ofthe one or more die comprises a passivation region for protection fromPEC etching.
 25. The method of claim 1, wherein each of the diecomprises one or more components, the one or more components beingselected from at least one of an electrical contact, a current spreadingregion, an optical cladding region, a laser ridge, a laser ridgepassivation, or a pair of facets, either alone or in any combination.26. The method of claim 1, wherein the gallium and nitrogen containingsubstrate is reclaimed and prepared for reuse after transferring.